This invention relates to improvements in furniture which is equipped with motors for producing vibrations which result in the user of the furniture experiencing a massaging effect.
A prior type of massaging furniture, particularly a chair, is disclosed in U.S. Pat. No. 3,653,375, dated Apr. 4, 1972, owned by the inventor of this application. In this patent, a pair of rotating electric motors are mounted to a rigid closed frame which is part of the chair. The motors are on opposite sides of the closed frame and have eccentric weights on their shafts. This causes the motors to vibrate during operation and to impart vibrations to the frame and, hence, to the user of the chair. The cited patent also discloses the concept of operating the motors at different speeds so they vibrate at different frequencies. The frequencies are selected such that interference waves are set up in the rigid member. This results in a soothing body massage being imparted to the user.
Although the above outlined massage furniture is basically satisfactory, it is not optimized in all respects. The best results are obtainable if the vibrational frequencies of the motors and, hence, their differential frequencies, are held within a comparatively small range under control of the user. Unfortunately, available small rotary motors exhibit speed variations as great as 10% or even more even if they are supplied from a constant and stable power supply. This inherent speed variation is often greater than the desired frequency differential between the motors which the user of the furniture is trying to establish by use of the electric controls.
Another disadvantage of rotating vibratory motors is that they have bearings which are subject to wearing and to freezing in which case their life might be terminated sooner than the life of the furniture itself. The cost of electric motors is also significant.
In accordance with the present invention, massaging furniture is equipped with nonrotating vibrating motors which are controlled to produce moving interference waves in the furniture. There have been some prior devices intended for contact with the human body in which only one nonrotating vibrating motor is used. Such prior devices are incapable of producing the interference waves which result in the subtle massaging effect which is desired. U.S. Pat. No. 2,920,618 discloses a vibratory therapeutic cushion in which a single nonrotating vibratory motor is used. The motor is mounted on a diaphragm which allows large amplitude vibrations to be produced which would probably not be suitable for furniture. U.S. Pat. No. 2,921,578 discloses a nonrotating vibratory motor wherein the vibrations are imparted to resilient springs in a chair structure. U.S. Pat. No. 2,943,621 discloses a vibratory motor mounted in a tube within a pillow. U.S. Pat. No. 3,043,294 shows a vibratory foot massaging machine with a nonrotating vibratory motor mounted on a diaphragm type footrest. U.S. Pat. No. 3,765,400 shows an exercising stand which has a spring mounted platform and a pair of motors for oscillating the platform up and down and sideways, respectively.